Method of manufacturing a molded multilayer article

ABSTRACT

Molten polymers are forced into T dies combined to form a multiple T die, the molten polymers are extruded through the T dies in monolayer. The monolayers extruded through the T dies are superposed and laminated outside the multiple T die while the polymers are in a molten or semi-molten state to form a intermediate molten multilayer. The multiple T die is advanced into a space between an open top half mold and a bottom half mold of a compression mold to deliver the intermediate multilayer onto the bottom half mold. The intermediate multilayer is cut to a predetermined length on the bottom half mold, and is processed for compression molding in the compression mold to form a multilayer article. A molding cycle for molding the multilayer article is carried out automatically at a remarkably improved manufacturing efficiency.

This is a Divisional of U.S. application Ser. No. 09/777,698, filed Feb.7, 2001, now U.S. Pat. No. 6,692,607, which is a Divisional of U.S.application Ser. No. 09/050,911, filed Mar. 31, 1998, now U.S. Pat. No.6,186,765, which claims priority from the prior Japanese PatentApplication Nos. 9-80868, filed Mar. 31, 1997; 9-80869, filed Mar. 31,1997; 9-80870, filed Mar. 31, 1997; 9-80871, filed Mar. 31, 1997 and9-309027, filed Nov. 11, 1997, the entire contents all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a moldedmultilayer article and an apparatus therefor. More specifically, thepresent invention relates to a method and an apparatus which is capableof efficiently producing molded multilayer article in a wide variety ofsizes and shapes by combining a process of laminating a plurality ofextruded molten polymer layers and a process of compression molding.

2. Description of the Related Art

Known processes of manufacturing a monolayer article of a thermoplasticpolymer adapt a combination of an injection molding process and a pressforming process, or a combination of an extrusion molding process and avacuum forming process for shaping a film or sheet into a article with arelatively broad width and a complicated three-dimensional shape.

A sheet is formed by extruding a molten polymer through an extrusiondie, and successively the sheet is fed to molds for a compressionmolding process. Therefore, the extrusion die and the associated partsmust be moved toward the molds. Various devices adapted for moving anextrusion die along a predetermined path over the bottom half mold of anopen mold have been disclosed, for example, in JPB No. 17931/1982 andJPA No. 137814/1988.

A stampable sheet molding process applied to processes for producingthat kind of sheet products is one of the known processes. In thestampable sheet molding process, a sheet formed by extrusion is cut intoa workpiece with a predetermined size, and the workpiece is softened byheating and delivered to final molding process on a compression moldingmachine. Such a processing method comprises steps of extrusion, forming,cutting process, heating process, and compression molding. However,additional electric power consumption is increased for heating processand limited varieties of shape of the products to be processed by thecompression molding is one of the drawbacks.

The extrusion die employed in those known techniques has a die slotopening of a fixed dimension. Therefore the extrusion die can be usedonly for extruding a sheet of a predetermined fixed width and is notapplicable to extrusion of a sheet with varying width and thickness.

An apparatus disclosed in JPB No. 25689/1989 is adapted for moldingfinished sheet products with varying width by extruding a sheet withvarying width, which is feed to compression molding machines.

This apparatus is capable of changing the sectional shape of a sheetwhich is extruded through a die disposed opposite to the compressionmolding machine according to the shape of an finished product.

The foregoing prior art techniques relate to monolayer articles. Onekind of molded articles has a structure of laminated layers consistingof sheets or films in different in strength, hardness, color or such.For example, one of molded multilayers articles consists of a baselayer, a mid-layer and a skin layer.

Prior art methods of manufacturing molded multilayer articles of theabovementioned kind and apparatus therefor are disclosed in JPB No.2491/1993 and JPA No.24128/1993. In these prior art, a multilayer sheetis formed by co-extruding molten polymers through a multilayer T (slot)die, and the multilayers sheet are fed to molds of a compression moldingmachine for the subsequent compression molding process.

Since the multilayer sheet is formed in the multilayer T die, it isdifficult to control the respective temperatures of the monolayer sheetsindividually. Particularly, it is difficult to hold the mid-layercontaining a foaming agent at a temperature which will not cause thefoaming agent to produce foams until the multilayer sheet is subjectedto a compression molding process because the mid-layer is heated by theadjacent layers of molten polymers and the T die.

A cutting process for a sheet formed by extruding molten polymer throughT die is disclosed in JPB No.44124/1985. In this cutting process, thesheet is cut to a length by moving a cutting blade in a directionperpendicular to the width of the sheet at the die slot opening of the Tdie.

When the sheet is cut by such a manner that the molten polymer has atendency to adhere to part of the T die around the die slot opening, thescorched polymer is liable to adhere to the surface of the sheet, thecutting blade becomes dull due to heating at a high temperature, and themolten polymer is liable to adhere also to the cutting blade during thesheet cutting process.

Because the molten polymer is in a state that has a low viscosity andhighly adhesive in a sheet cutting process, difficulty in cutting thesheet by the cutting blade will be enhanced. Therefore, a cleaning meansmust be disposed near the cutting blade and the cutting blade needsrelatively frequent cleaning so that the molten polymer may not adhereto the cutting blade kept on standby near the die slot opening of the Tdie.

Cleaning of the cutting blade increases the molding cycle time andreduces the efficiency of the manufacturing process greatly. If thecutting blade is not kept satisfactorily clean, the quality of moldingswill be deteriorated.

The improvement of the efficiency of processes for manufacturing moldedmultilayersheet parts of complicated shapes has been a main problem thatfaces manufacturers. Particularly, in a case that a multilayer articleconsists of component sheets differing from each other in material,thickness and shape, it is impossible to achieve a series of processesincluding a extrusion process, a laminating process, a cutting processand a compression process by single reciprocating stroke of the T die.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amolded multilayer article manufacturing method which is capable ofautomatically carrying out a molding cycle including an extrusionprocess of extruding a plurality of monolayers through a plurality of Tdies, a forming process of superposing and laminating the plurality ofmonolayers, and a compression molding process for a finished article ofdesired shape, and of carrying out the molding cycle at a very highmanufacturing efficiency, and to provide a multilayersheet moldingmanufacturing apparatus for carrying out the method.

A second object of the present invention is to provide a moldedmultilayer article manufacturing method and apparatus capable ofefficiently manufacturing a multilayer article consisting of a pluralityof monolayers differing from each other in width, shape and such.

A third object of the present invention is to provide a method andapparatus capable of feeding a plurality of molten monolayers extrudedthrough a plurality of T dies and quickly and smoothly cutting it to adesired length for a compression molding process to improvemanufacturing efficiency.

According to one aspect of the present invention, a method formanufacturing a molded multilayer article by molding a multilayer sheetconsisting of a plurality of polymer layers, comprises the steps of:extruding a plurality of monolayers of molten polymers by forcing themolten polymers into a multiple T die combined with a plurality of Tdies so that the molten polymers are extruded respectively through the Tdies; forming an intermediate molten multilayer by superposing andlaminating the monolayers extruded through the T dies outside themultiple T die while the polymers are in a molten state or a semi-moltenstate; feeding the intermediate molten multilayer to a compression moldhaving the bottom half mold and a top half mold by advancing themultiple T die into a space between the bottom half mold and the tophalf mold;

cutting the intermediate molten multilayer to a predetermined length;and molding the intermediate molten multilayer in the compression moldinto a multilayer article of a desired shape.

According to another aspect of the present invention, an apparatus formanufacturing a molded multilayer article by molding a multilayer sheet,comprises: a plastication means for separately plasticating polymers forforming each of monolayers, and feeding molten polymers by pressure; amultiple T die combined with a plurality of T dies for extruding themonolayers and jointed to the plastication means; moving means formoving the plastication means and the multiple T die all together; alaminating means provided with the multiple T die to form a intermediatemolten multilayer by superposing and laminating the monolayers extrudedin molten or semi-molten state; a cutting means provided with themultiple T die for cutting the intermediate molten multilayer in apredetermined length; and a compression molding means provided with amold for molding the intermediate molten multilayer into a finishedmultilayer article of a desired shape.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description takenin connection with the accompanying drawings, in which:

FIG. 1 is a schematic side view of a molded multilayer articlemanufacturing apparatus in a first embodiment according to the presentinvention;

FIG. 2 is a schematic plan view of the molded multilayer articlemanufacturing apparatus in the first embodiment shown in FIG. 1;

FIG. 3 is an enlarged sectional view of an essential part of a multipleT die included in the molded multilayer article manufacturing apparatusin the first embodiment shown in FIG. 1;

FIG. 4 is a schematic view, similar to FIG. 3, of assistance inexplaining a mode of feeding multilayers extruded through the multiple Tdie of FIG. 3 to a bottom half mold of a compression mold of acompression molding machine;

FIG. 5 is a typical longitudinal sectional view of an essential part ofthe molded multilayer article manufacturing apparatus in the firstembodiment shown in FIG. 1;

FIG. 6 is a schematic sectional view showing an intermediate multilayersobtained by cutting a multilayers and fed to the bottom half mold of thecompression mold;

FIG. 7 is a block diagram of a sequential control system for theautomatic sequential control of the molten multilayer articlemanufacturing apparatus in the first embodiment shown in FIG. 1;

FIGS. 8( a) to 8(e) are perspective views of molded multilayer articleof different shapes manufactured by the first embodiment shown in FIG.1;

FIG. 9 is a schematic view of a die slot opening adjusting mechanism;

FIG. 10 is a block diagram of an open-loop control system included inthe molded multilayer article manufacturing apparatus in the firstembodiment shown in FIG. 1;

FIG. 11 is a block diagram of a closed-loop control system included inthe molded multilayer article manufacturing apparatus in the firstembodiment shown in FIG. 1;

FIG. 12 is a time chart of assistance in explaining the sequentialoperations of mechanisms included in the molded multilayer articlemanufacturing apparatus in the first embodiment shown in FIG. 1;

FIG. 13 is a schematic sectional view of a sheet cutting mechanismincluded in the molded multilayer article manufacturing apparatus in thefirst embodiment shown in FIG. 1;

FIG. 14 is a schematic sectional view of the sheet cutting mechanism ofFIG. 13 in a cutting operation;

FIG. 15 is a schematic side view of assistance in explaining thearrangement of the sheet cutting mechanism of FIG. 13;

FIG. 16 is a perspective view of assistance in explaining a sheetcutting operation of a cutting blade included in the sheet cuttingmechanism of FIG. 13;

FIG. 17 is a schematic sectional view of a sheet cutting mechanism forcutting a monolayer;

FIG. 18 is a schematic sectional view of a sheet cutting mechanismincluded in a molded multilayer article manufacturing apparatus in asecond embodiment according to the present invention;

FIG. 19 is a schematic sectional view of the sheet cutting mechanism ofFIG. 18 in a cutting operation;

FIG. 20 is a schematic plan view of assistance in explaining thearrangement of the sheet cutting mechanism of FIG. 18;

FIG. 21 is a perspective view of assistance in explaining a sheetcutting operation of a cutting blade included in the sheet cuttingmechanism of FIG. 18;

FIG. 22 is a schematic sectional view of a sheet cutting mechanismincluded in a molded multilayer article manufacturing apparatus in athird embodiment according to the present invention;

FIG. 23 is a schematic perspective view of the sheet cutting mechanismof FIG. 22;

FIG. 24 is a schematic sectional view of a modification of the sheetcutting mechanism of FIG. 22;

FIG. 25 is a schematic perspective view of the sheet cutting mechanismof FIG. 24;

FIGS. 26( a), 26(b) and 26(c) are schematic sectional views of a sheetcutting mechanism included in a molded multilayer article manufacturingapparatus in a fourth embodiment according to the present invention indifferent phases of operation;

FIG. 27 is a schematic plan view of assistance in explaining thearrangement of the sheet cutting mechanism of FIG. 26;

FIG. 28 is a schematic sectional view of a sheet cutting mechanismincluded in a molded multilayer article manufacturing apparatus in afifth embodiment according to the present invention; and

FIG. 29 is a schematic perspective view of the sheet cutting mechanismof FIG. 28.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods of manufacturing a molded multilayer article and apparatustherefor in accordance with the present invention will be describedhereinafter with reference to the accompanying drawings.

1. Molded Multilayer Article Manufacturing Apparatus

FIGS. 1 to 7 show a molded multilayer article manufacturing apparatus ina first embodiment according to the present invention. The firstembodiment will be described as applied to manufacturing a moldedarticle with three layers. Numeral 10 represents a plastication meansfor plasticating a polymer material for each of the layers and applyingpressure to each molten polymer to force it out. As shown in FIG. 2, aninjection molding machine acting as the plastication means 10 isprovided with three injection units 10 a, 10 b and 10 c disposed in aparallel arrangement. The injection units 10 a, 10 b and 10 c havedelivery nozzles 12 a, 12 b and 12 c, which are connected to T dies 14a, 14 b and 14 c(a slot die is referred to as the T die) respectively.The molten polymer is pushed through the T die 14 a, 14 b and 14 c thatshapes the molten polymer into a molten monolayer, respectively.

As shown in FIG. 9, the T dies 14 a, 14 b and 14 c are provided withdeckles for adjusting slot opening to adjust the widths of the moltenmonolayer extruded through the slot openings of the T dies 14 a, 14 band 14 c, respectively. The T dies 14 a, 14 b and 14 c are assembled toconstruct a multiple T die 14. The polymer are formed into the moltenmonolayers by the extrusion through the T dies 14 a, 14 b and 14 c ofthe T die 14 in a molten state or a semi-molten state. The polymerlayers of the molten or semi-molten polymer are laminated to form aintermediate molten multilayer 16.

The intermediate molten multilayer 16 is cut to a predetermined length,and fed to a compression molding machine 18. The compression moldingmachine 18 is provided with a mold consisted of a top half mold 24 a anda bottom half mold 24 b, and a mold clamping mechanism to move the tophalf mold 24 a vertically relative to the bottom half mold 24 b and toclose the mold tightly. The intermediate molten multilayer 16 is placedon the bottom half mold 24 b, and then the top half mold 24 a compressesthe intermediate multilayer against the bottom half mold 24 b to shapeit into a desired form.

Referring to FIG. 1, the injection units 10 a, 10 b and 10 c are mountedon a base 19 placed on a bed 17. The base 19 can be horizontallyreciprocated by a base moving mechanism 22 provided with a drive motor(not shown) and rack and pinion mechanism (not shown), which are builtin the bed 17. The multiple T die 14 is reciprocated together with thebase 19 from a standby position indicated by continuous lines in FIG. 1to a space between the open top half mold 24 a and the bottom half mold24 b of the compression molding machine 18. A position of the multiple Tdie 14 indicated by alternate long and a short dash lines in FIG. 1 isthe foremost position of the multiple T die where the feed of theintermediate molten multilayer to the bottom half mold 24 b is started.

Thus, the multiple T die 14 can be moved together with the injectionunits 10 a, 10 b and 10 c into and out of the space between the open tophalf mold 24 a and the bottom half mold 24 b.

Referring to FIG. 3, a laminating mechanism 26 is disposed near the slotopenings of the multiple T die 14 integrally therewith. The laminatingmechanism 26 forms the intermediate molten multilayer 16 by laminatingmolten monolayers 16A, 16B and 16C extruded through the T dies 14 a, 14b and 14 c respectively. The laminating mechanism 26 is disposedupstreams of a cutting mechanism 20 for cutting the intermediate moltenmultilayer 16 to a predetermined length with respect to a direction inwhich the intermediate molten multilayer 16 is delivered. The laminatingmechanism 26 is provided with a pair of nip rollers 26 a and 26 b whichsandwiches the mid-monolayer 16C between the outer monolayer 16A and 16Bin a manner such that air may not be trapped between each monolayer 16A,16B and 16C. Cylinder actuators 27 a and 27 b are connected to operatethe nip rollers 26 a and 26 b. When the nip rollers 26 a and 26 b movestoward each other, the monolayers 16A, 1613 and 16C are pressed betweenthe nip rollers 26 a and 26 b to form them into the laminatedintermediate molten multilayer 16.

The laminating mechanism 26 is capable of dealing with a laminatingoperation for a predetermined intermittent pattern for forming anintermediate molten multilayer comprising pieces of the monolayers 16A16B and 16C of different lengths. Multilayer articles having suchintermittent patterns and shapes can be manufactured by moving the niprollers 26 a and 26 b toward and away from each other according to thepattern.

The cutting mechanism 20 is disposed below the slot openings of themultiple T die 14 to cut off the intermediate molten multilayer 16. Thecutting mechanism 20 and the laminating mechanism 26 are combined withthe multiple T die 14 and are moved together with it. As shown in FIG.5, the cutting mechanism 20 has a pair of cutting blades disposed on theopposite sides of the intermediate molten multilayer 16 to nip it off.Any suitable one of various modifications, which will be describedlater, of the cutting mechanism 20 may be employed.

FIG. 5 is a longitudinal sectional view showing an essential part of themultilayer article manufacturing apparatus and the arrangement of limitswitches for the positioning of the multiple T die 14 and for thesequential control of operations of the component mechanisms of theapparatus. FIG. 7 is a block diagram for an automatic sequential controlsystem.

Referring to FIG. 5, a limit switch LS includes contacts 1 to 4 disposedon the bed 17. A contact operating member 30 for operating the contacts1 to 4 is attached to the base 19 on which the injection units 10 a, 10b and 10 c are mounted. The contact operating member 30 closes and opensthe contacts 1 to 4 of the limit switch LS according to the position ofthe multiple T die 14 as the base 19 is moved. The contacts 1 to 4 ofthe limit switch LS correspond, respectively, to positions LS1 to LS4 onthe bottom half mold 24 b of the compression molding machine 18. Signalsindicating the condition of the contacts 1 to 4 of the limit switch LSare sent from the base moving mechanism 22 to a sequencer 34. Then thesequencer 34 executes a sequential control program on the basis of theinput signals to control the operational sequence of the multilayerarticle manufacturing apparatus.

In the first embodiment, when the base 19 moves forward and the contact1 of the limit switch LS is closed by the contact operating member 30,the slot openings of the multiple T die is located at a positiondirectly above the position LS1 on the bottom half mold 24 b. When themultiple T die 14 is moved backward, and the contact 2, 3 or 4 of thelimit switch LS is closed, an end portion of the intermediate moltenmultilayer cut by the cutting mechanism 20 corresponds to the positionLS2, LS3 or LS4. When the multiple T die 14 is at a position shown inFIG. 5, the contact 3 of the limit switch LS is closed. If theintermediate molten multilayer 16 is cut off by the cutting mechanism 20at the moment when the contact 3 of the limit switch LS is closed, thecutting end lie at the position LS4 on the bottom half mold 24 b.

In FIG. 5, indicated at 31 is an injection cylinder actuator foradvancing screws 11 a, 11 b and 11 c of the injection units 10 a, 10 band 10 c to deliver the molten polymer to the multiple T die 14.

FIG. 7 shows the sequential control system including the sequencer forcontrolling process elements of the multilayer article manufacturingapparatus. The shape patterns of each layers of the multilayer articlecan be specified by operating a setting panel 35. A central processingunit (CPU) 32 executes a sequential control program specifying thesequence of processes to be carried out according to the specified shapepatterns, and gives instructions to the sequencer 34. Then the sequencer34 controls operative sequences of the process elements according to theinstructions given thereto.

The T dies 14 a, 14 b and 14 c of the multiple T die 14 are providedwith adjusting devices 42 a, 42 b and 42 c, which will be describedlater, for adjusting the widths of the layers 16A, 16B and 16C extrudedthrough the slot openings of the T dies 14 a, 14 b and 14 c,respectively. The adjusting devices 42 a, 42 b and 42 c are controlledby the sequencer 34.

The compression molding machine 18 is provided with a mold exchangingdevice 36 and a mold heating/cooling device 38 which are controlled bythe sequencer 34.

The operations in the multilayer article manufacture will be describedhereinafter with reference to FIGS. 5 to 7.

Referring to FIG. 5, the screws 11 a, 11 b and 11 c of the injectionunits 10 a, 10 b and 10 c of the plastication means 10 are advanced toforce the molten polymer through the delivery nozzles 12 a, 12 b and 12c into the T dies 14 a, 14 b and 14 c of the multiple T die 14. Themolten polymer is formed into the molten monolayers 16A, 16B and 16C byextrusion through the T dies 14 a, 14 b and 14 c.

The multiple T die 14 continues to extrude the monolayer 16A, 16B and16C, while the injection unit 10 a, 10 b and 10 c together with the base19 is advanced to move the multiple T die 14 into the space between theopen top half mold 24 a and the bottom half mold 24 b. The monolayers16A, 16B and 16C are superposed and laminated between the nip rollers 26a and 26 b disposed below the multiple T die 14 to form the intermediatemolten multilayer 16.

The multiple T die 14 is advanced further into the space between the tophalf mold 24 a and the bottom half mold 24 b, until the multiple T die14 arrives at the position directly above the position LS1 where contact1 of the limit switch LS is switched on. Consequently, the end portionof the intermediate molten multilayer 16 hanging from the multiple T die14 falls upon the position LS1 on the bottom half mold 24 b.

The sequencer 34 gives an instruction to the base moving mechanism 22 toretreat the multiple T die 14. While retreating, the intermediate moltenmultilayer 16 is extruded continuously through the multiple T die 14 soas to be placed onto the bottom half mold 24 b.

Upon the arrival of the multiple T die 14 at a position directly abovethe position LS3 (FIG. 5), the contact 4 of the limit switch LS isswitched on and an on-signal is given to the sequencer 34. The sequencer34 actuates the cutting mechanism 20 to cut off the intermediate moltenmultilayer 16 to a predetermined length. When the cut end portion of theintermediate molten multilayer 16 is placed onto the position LS4, thedelivery of the intermediate molten multilayer 16 to the bottom halfmold 24 b is completed.

Thus, the laminating process of the monolayers 16A, 16B and 16C extrudedthrough the multiple T die 14 and the delivery of the intermediatemolten multilayer 16 to the bottom half mold 24 b is accomplished withone motion of the base moving mechanism 22.

Since the monolayers 16A, 16B and 16C in molten state are superposed andcut, the cut edges of the monolayers 16A, 16B and 16C can be weldedtogether. Therefore, the end portion of the intermediate moltenmultilayer 16 can be easily set on the bottom half mold 24 b for thenext compression molding cycle, and the yield rate can be improved.

In a compression molding process, namely, the last process, the top halfmold 24 a is lowered to compress the intermediate molten multilayer 16between the top half mold 24 a and the bottom half mold 24 b to form itinto the desired shape as a multilayer article.

It is preferable to assemble the T dies 14 a, 14 b and 14 c so that theintermediate molten multilayer 16 with the thickest or heaviestmonolayer 16B as a lower most layer is delivered to the bottom half mold24 b as shown in FIG. 4. When the T dies 14 a, 14 b and 14 c areassembled so as to meet the foregoing requirement, it is preferable todispose the T die 14 b connected to the injection unit 10 b, so that thedelivery nozzle 12 b is the shortest among the delivery nozzles 12 a, 12b and 12 c, as shown in FIG. 2, to force the molten polymer into the Tdie 14 b at a low pressure loss and to save space.

2. Structural Patterns of Multilayer Articles

Multilayer articles of various shapes that can be manufactured by thepresent invention will be described with reference to FIGS. 8( a) to8(e).

Structure 1

A multilayer article 40 a shown in FIG. 8( a) is a three layer structureconsisting of a first monolayer 16A serving as a skin layer, a secondmonolayer 16B serving as a base layer, and a third monolayer 16C servingas an mid-layer, and the monolayers 16A, 16B and 16C have the same shapeand made of the same thermoplastic polymer, such as a polyolefin.

Structure 2

A multilayer article 40 b shown in FIG. 8( b) is a three layer structureconsisting of monolayers 16A, 16B and 16C respectively having differentshapes. The monolayers 16A, 16B and 16C have different shapes in respectof the width pattern, respectively. The adjusting devices 42 a, 42 b and42 c included in the T dies 14 a, 14 b and 14 c are controlled so as tovary the widths of the monolayers 16A, 16B and 16C according to thepatterns as shown in FIG. 8( b) to form the multilayer article 40 bhaving layers in different width patterns.

Structure 3

A multilayer article 40 c is a two layers structure consisting ofmonolayers 16A and 16C serving as a surface layer, and a monolayer 16Bserving as a base layer. The monolayers 16A and 16C have a differentcolor or made of a material different from each other.

Structure 4

A multilayer article 40 d shown in FIG. 8( d) is a three layersstructure consisting of a monolayer 16A serving as a skin layer, amonolayer 16B serving as a base layer, and a monolayer 16C serving as amid-layer. The length of the monolayer 16A is shorter than those of themonolayer 16B and 16C. While laminating the monolayers 16A, 16B and 16C,only the monolayer 16A is cut to a predetermined shorter length by thecutting mechanism 20, and the feed of the molten polymer by theinjection unit 10 a to the T die 14 a through which extrudes themonolayer 16A is suspended. This process enables to form the multilayerarticle 40 d partly varying in the number of layers easily.

Structure 5

A multilayer article 40 e shown in FIG. 8( e) is a three layersstructure consisting of a monolayer 16A serving as a skin layer, amonolayer 16B serving as a base layer, and a monolayer 16C serving as amid-layer made of a foaming polymer. The monolayers 16A, 16B and 16Chave the same shape.

The polymer material used for forming the mid-layer 16C contains afoaming agent. The injection unit 10 c plasticates the polymer materialat a relatively lower temperature which does not cause the foaming agentto generate a gas, and then feeds the polymer material to the T die 14c. The temperatures of the molten polymer forming the skin layer 16A andthe base layer 16B are higher than that of the molten polymer for themid-layer 16C by temperatures in the range of 50 to 100° C.

As is obvious from FIGS. 3 and 4, the multiple T die 14 is not anintegrated die which is composed of the T dies 14 a, 14 b and 14 c, butan assembly of the component T dies 14 a, 14 b and 14 c. Therefore, theT die 14 c interposed between the T dies 14 a and 14 b is safe from heatconduction due to the direct contact, and the temperatures of the T dies14 a, 14 b and 14 c can be independently controlled. Since the moltenpolymers extruded through the T dies 14 a, 14 b and 14 c are laminatedoutside below the multiple T die 14, the temperature of the moltenpolymer extruded through the T die 14 c can be maintained at arelatively low temperature that will not cause the foaming agent togenerate a gas. Therefore, the intermediate molten multilayer 16 is fedto the compression molding machine 18 in a state where the molten layer16C is kept unfoamed.

As shown in FIG. 5, the intermediate molten multilayer 16 is compressedbetween the top half mold 24 a and the bottom half mold 24 b to mold itinto the desired shape for the finished part. The clamped mold isdetached from the compression molding machine 18 and replaced withanother mold by the mold exchanging device 36. The detached mold isheated by the heating/cooling unit 38 at a predetermined temperaturewhere the layer 16C foams.

Preferably, the mold exchanging device 36 replaces a mold 24A in whichthe molten layer 16C is foaming with an empty mold, because foamingprocess take sufficient time. By that means, the mold 24A can be kept inthe foaming process sufficient to foam the layer 16C satisfactorily.After the completion of foaming of the layer 16C, the mold 24A is cooledbefore the multilayer article 40 e is ejected from the mold 24A. Thus,the mid-layer 16C is kept unfoamed while the molten layers 16A, 16B and16C are laminated. And the layer 16C is made to foam during thecompression molding process to improve the moldability with an excellentaesthetic appearance.

Furthermore, the mold exchanging device 36 enable the compressionmolding machine 18 to start the next molding cycle immediately, so thatthe multilayer article 40 e can be manufactured efficiently.

3. Automatic Width Control Operation for the Width Adjusting Mechanismsin the T Dies

The automatic control for the width adjusting mechanisms 42 a, 42 b and42 c to manufacture the multilayer article in various shapes will bedescribed hereinafter.

FIG. 9 shows the width adjusting mechanism 42 a disposed in the T die 14a. The width adjusting mechanism 42 b and 42 c disposed respectively inthe T dies 14 b and 14 c are the same as the width adjusting mechanism42 a shown in FIG. 9 and hence only the width adjusting mechanism 42 awill be described.

Referring to FIG. 9, a pair of decides 52 a and 52 b are fitted into aslot opening 50 of the T die 14 a so as to be movable in the transversedirection of the molten layer being extruded through the T die 14 a. Thedecides 52 a and 52 b are moved simultaneously toward or away from eachother to adjust the length of the slot opening 50.

Each of the decides 52 a and 52 b is driven by a deckle moving mechanismprovided with a servomotor 54. Only the decide moving mechanism and theservomotor 54 for moving the deckle 52 b is shown in FIG. 9. A driveshaft of the servomotor 54 is coupled to a ball screw 58 by a shaftcoupling 56. A slider 60 provided with a ball nut is connected to oneend of the decide 52 b and is supported slidably on guide rods 62 a and62 b. The ball screw 58 is engaged with the ball nut included in theslider 60. The servomotor 54 drives the ball screw 58 for rotation tomove the slider 60 along the guide rods 62 a and 62 b, so that thedeckle 52 b is moved linearly along the slot opening 50 of the T die 14a.

The positions and velocity of the deckles 52 a and 52 b can becontrolled by controlling the servomotors 54. While the molten polymeris being extruded through the slot opening 50, the deckles 52 a and 52 bare held at a predetermined position to shape the molten polymer intothe molten layer in a desirable width. Continuous control of thepositions of the deckles 52 a and 52 b while extrusion through the slotopening 50 makes it possible to vary the molten layer in widthcontinuously.

Methods of controlling the positions and velocity of the deckles 52 aand 52 b will be described below.

Open-Loop Control Method

FIG. 10 shows an open-loop control system for the positional control ofthe deckles to form the multilayer article in the shapes shown in FIGS.8( a) to 8(e).

As mentioned above with reference to FIG. 5, the respective positions ofthe injection molding machine 10 (injection units 10 a, 10 b and 10 c)and the multiple T die 14 (T dies 14 a, 14 b and 14 c) are detected byany one of the contacts 1 to 4 of the limit switch LS, and the sequencer34 controls operation for extruding the molten polymers according to theposition of the multiple T die 14.

The CPU 32 produces instructions to be given to the sequencer 34 on thebasis of the data set by a setting panel 35 regarding to the shape ofthe multilayer article. The sequencer 34 gives position (velocity)instructions to the servomotors 54 for the open-loop control of thepositions (velocity) of the deckles 52 a and 52 b.

The sequencer 34 controls a flow regulating solenoid valve 39 toregulate the flow rate of a hydraulic fluid supplied to the injectioncylinder 31. The injection cylinder 31 makes the screws 11 a, 11 b and11 c move forward at a predetermined speed to feed the molten polymer ata predetermined delivery rate. By controlling the delivery rate to besubstantially proportional to the change rates at which the widths ofthe molten layers are changed by the control of the positions (speeds)of the deckles 52 a and 52 b, only the width of the molten layers eachextruded through the T dies 14 a, 14 b and 14 c can be controlled withthe molten layers kept in a constant thickness.

In an embodiment in which extruders for continuous extrusion as theplastication means are employed instead of the injection unit 10, therotating rate of the screws of the extruders are controlled to vary thedelivery rates of the molten polymer.

Closed-Loop Control Method

FIG. 11 shows a closed-loop control system for the positional control ofthe deckles to form the multilayer article in the shapes shown in FIGS.8( a) to 8(e).

Program data for varying the widths of the molten layers according tothe shape of a multilayer article is prepared by using the setting panel35. The CPU 32 gives position instruction signal of the deckles 52 a and52 b in accordance with the shape of the part through the sequencer 34to the servomotors 54. Consequently the positions (velocities) of thedeckles 52 a, 52 b fitted in the T dies 14 a, 14 b and 14 c respectivelycan be continuously adjusted to vary the respective widths of the moltenlayers during the extrusion.

The positions and the velocities of the decides 52 a and 52 b aredetected by encoders 66 connected to the servomotors 54, and theencoders 66 feed back the detection signals to the sequencer 34 for afeedback control operation. Sensors 68 which detect the positions andthe velocities of the screws of the injection units 10 a, 10 b and 10 cfeed back signals to the sequencer 34 for a feedback control operation.The detected positions (velocities) of the deckles 52 a and 52 brepresented by the feedback signals are compared with the instructedpositions (velocities) in order to make the deckles 52 a and 52 b followto the instructions. And the sequencer 34 compares the detectedpositions (velocities) of the screws 11 a, 11 b and 11 c with theinstructions to control the flow rate of the hydraulic fluid suppliedthrough the flow regulating valve 39 to the injection cylinder 31. Thus,the delivery rates at which the molten polymers are delivered by theinjection units 10 a, 10 b and 10 c are successively controlled.

In an embodiment in which extruders for continuous extrusion as theplastication means are employed instead of the injection unit 10, therotating rate of the screws of the extruders are controlled to vary thedelivery rates of the molten polymer.

4. Example of Sequential Control Program for Multilayer ArticleManufacturing

A sequential control program for the automatic manufacture of themultilayer article will be described by way of example with reference toFIG. 12.

FIGS. 12( b), 12(c) and 12(d) are time sharing charts of a sequentialcontrol program for a multilayer article shown in FIG. 12( a), showing aseries of operations for the deckles 52 a and 52 b, the injection units10 a, 10 b and 10 c, the cutting mechanism 20 and the laminatingmechanism 26. In this example, the multilayer article consists ofmonolayers 16A, 16B and 16C.

FIG. 12( b) shows a time sharing chart for the monolayer 16A shortest inlength. The position (velocity) of the deckles 52 a, 52 b, theplastication operation of the injection unit 10 a, the cutting operationof the cutting mechanism 20, and the laminating operations of thelaminating mechanism 26 in one fabrication cycle are controlled tofollow in the series of sequences given in the time sharing chart inFIG. 12( b).

FIG. 12( c) shows a time sharing chart for the monolayers 16B and 16C ofthe same length. The position (velocity) of the deckles 52 a, 52 b, theplastication operations of the injection unit 10 b and 10 c, the cuttingoperation of the cutting mechanism 20, and the laminating operations ofthe laminating mechanism 26 in one fabrication cycle are controlled tofollow in the series of sequences given the time sharing chart in FIG.12( c).

Since the monolayer 16A is shorter than the monolayers 16B and 16C inlength, the operational sequences of the injection unit 10 a and thedeckles 52 a, 52 b are determined so that the extrusion of the monolayer16A is scheduled to suspend during the continuous extrusion of themonolayers 16B and 16C. While the monolayers 16A, 16B and 16C arelaminated together, the layer 16A exclusive of layers 16B and 16C is cutoff to a predetermined length upon the suspension of the extrusionthereof. As for the rest layers, the monolayers 16B and 16C are extrudedcontinuously up to the completion of extrusion when the monolayers 16Band 16C are cut off to a predetermined length longer that that of thelayers 16A.

It is noted that the monolayers 16A, 16B and 16C which are uniform inthickness are formed during the extrusion. For that purpose, thedecrease rates of the feed of the molten polymer from the injectionunits 10 a, 10 b and 10 c correspond to the reducing rates at which thedeckles 52 a and 52 b regulate the slot opening lengths of the T dies 14a, 14 b and 14 c to narrow the monolayers 16A, 16B and 16C.

FIG. 12( d) shows a time sharing chart for the multilayer article ofwhich the monolayer 16C is not uniform in thickness. The delivery rateat which the injection unit 10 c delivers the molten polymer to extrudethe layer 16C is regulated in a manner as shown in FIG. 12( d).

5. Modifications of the Cutting Mechanism

Modifications of the cutting mechanism will be described hereinafter.

Cutting Mechanism in First Modification

FIG. 13 shows a cutting mechanism 100 for cutting the intermediatemolten layer to provide an given length, and FIG. 14 shows the cuttingmechanism 100 in operation.

The cutting mechanism 100 is disposed downstream of the laminatingmechanism 26 with respect to a feed direction. The cutting mechanism 100is provided with a pair of pad members 110 disposed opposite to, eachother to press the intermediate molten multilayer 16 therebetween. Anopposite end surface of each pad member 110 has a spherical surfaceadaptable for introducing the intermediate molten multilayer 16 incontact with it. In this embodiment, each pad member 110 is divided intoa pair of half pads 110 a and 110 b disposed one over the othersymmetrically with a narrow space 120 formed therebetween. The padmembers 110 each comprising the half pads 110 a and 110 b are connectedto driving devices 112, such as a hydraulic cylinder.

Preferably, the spherical surfaces of the pad members 110 to be broughtinto contact with the intermediate molten multilayer 16 are coated withanti-adhesive coatings, respectively, to prevent the molten polymer fromadhering to the surfaces of the pad members 110. Passages 116 as acooling means through which a coolant is circulated are provided in thebody of the pad members 110 to cool the heated portion of the padmembers 110 in contact with the intermediate molten multilayer 16.

The pad members 110 are provided with air passages 118, as an airblowing means, open into the spherical surfaces thereof to blowcompressed air toward the surface of the intermediate molten multilayer16 in order to facilitate the removal from the surfaces of the padmembers 110. The space 120 is confined between the opposite walls of thehalf pads 110 a and 110 b. The spherical surfaces of the half pads 110 aand 110 b are formed so as to protrude toward the intermediate moltenmultilayer 16, and the space 120 is located between the walls whichintersect the top contact surface of the half pads 110 a and 110 b.Either of the pad members 110 is provided with a cutting blade 122disposed in the space 120 between the half pads 110 a , and the cuttingblade can stick out from the spherical surface of the half pads towardthe intermediate multilayer 16. The cutting blade 122 has a cutting edge122 a and is positioned so that the cutting edge 122 a projects slightlyfrom the spherical surfaces of the half pads 110 a and 110 b. Thecutting blade 122 is connected to a cutter running device 124 whichmoves the cutting blade 122 in the transverse direction of theintermediate molten multilayer 16 to cut it of to a given length.

FIG. 15 shows the cutter running device 124 in more detail. The cuttingblade 122 is attached to a linear actuator 128 which moves slidably on aguide bar 126 disposed parallel to the transverse direction of theintermediate molten multilayer 16.

The function of the cutting mechanism 100 will be described below.

While the molten monolayers 16A, 16B and 16C are extruded through the Tdies 14 a, 14 b and 14 c of the multiple T die 14, the nip rollers 26 aand 26 b of the laminating mechanism 26 laminate them together to formthe intermediate molten multilayer 16 by nipping the monolayers 16A, 16Band 16C therebetween. The laminated multilayer 16 travels downwardlythrough the space between the pad members 110 of the cutting mechanism100.

When the actuators 112 are actuated to advance the pad members 110, theintermediate molten multilayer 16 is held between the pad members 110 ata position of 30 to 100 mm below the slot openings of the T dies 14 a,14 b and 14 c as shown in FIG. 14.

Although the intermediate molten multilayer 16 is in the the molten orsemi-molten state as a whole, a small portion thereof in contact withthe pad member 110 may be cooled by the cooling effect of the coolantflowing through the passages 116. A shaded part shown in FIG. 16 is thecooled portion of the intermediate molten multilayer 16. The cuttingblade 122 is disposed so as to be opposite closely to the cooled portionof the intermediate molten multilayer 16. When the cooled portion of theintermediate molten multilayer 16 is solidified into a state sufficientto cut it off easely, the cutter running device 124 commences movementof the cutting. Consequently, the cutting blade 122, which has been onstandby, travels transversely to cut off the intermediate moltenmultilayer 16 to a predetermined length.

According to the cutting mechanism 100, only the cooled portion of theintermediate molten multilayer 16, including a cutting line, is cooledto semi-solid stated so that the cooled portion 16 can be easily cutalong the cutting line. Therefore, the intermediate molten multilayer 16can be quickly and smoothly cut without remaining the adhesion of themolten polymer to the cutting edge 122 a of the cutting blade 122. Asthe cut edges of the monolayers 16A, 16B and 16C can be securely adheredto each other, the leading edge of the intermediate molten multilayer 16can be easily set on the molds for the next compression molding cycle.

During the cutting process, the molten intermediate multilayer 16 is cutwith the cutting blade 122 while the same is pressed between the presserpads 110, so that air may not enter into clearances between thelaminated monolayers 16A, 16B and 16C.

When retracting the pad member 110 by the driving actuator 112 after theintermediate molten multilayer 16 has been cut, compressed air is jettedthrough the air passages 118 against the intermediate molten multilayer16. Air blowing at the start of retraction of the pad member 110 enablesthe intermediate molten multilayer 16 to peel off from the surfaces ofthe pad member 110. Therefore, it is possible to avoid the firm adhesionof the intermediate molten multilayer 16 to the surfaces of the padmember 110.

As for a shape of the half pads 110 a and 110 b of the pad member 110having cooling capability of the cutting mechanism 100, a pair of halfpads which has a shape of a roller may be used.

FIG. 17 shows a cutting mechanism 106 which is applied to cutting amonolayer 102.

As shown in FIG. 17, the monolayer 102 extruded through a T die 104 iscut by the cutting mechanism 106. Thus, the monolayer 102 can be easilyand smoothly cut by the cutting mechanism 106 of the same constructionas the cutting mechanism 100 of FIG. 13.

Cutting Mechanism in Second Modification

FIGS. 18 and 19 show a second modification of the cutting mechanism 100of FIG. 13. A cutting mechanism 140 is provided with a pair of padmembers 110 which ate the same as those of FIG. 13. The intermediatemolten multilayer 16 is held between the pad members 110 when the sameis cut. In FIGS. 18 and 19, parts like or corresponding to those of thecutting mechanism 100 of FIG. 13 are designated by the same referencecharacters and the description thereof will be omitted.

In the cutting mechanism 140, a metal thin plate 142 for use as acutting blade is disposed in the space 120 between the half pads 110 aand 110 b of one of the pad members 110. The metal thin plate 142 has alength greater than the width of the intermediate molten multilayer 16.The metal thin plate 142 is held in the space 120 so as to be projectedfrom the surface of the pad member 110 which is brought into contactwith the intermediate molten multilayer 16. As shown in FIG. 20, themetal thin plate 142 is held at its opposite ends on holding members 144which are connected to actuators 146 (cutter operating means), such ashydraulic cylinders. The actuators 146 advance the metal thin plate 142in the space 120 toward the intermediate molten multilayer 16 so thatthe cutting edge of the metal thin plate 142 projects from the surfaceof the pad member 110.

A metal wire, such as a piano wire, may be used instead of the metalthin plate 142 for cutting the intermediate molten multilayer 16. Theintermediate molten multilayer 16 can be easily cut with the metal thinplate 142 or a metal wire being heated by a heater built in the padmember 110. It is effective to use, as the metal wire, a nichrome wireor the like which generates heat when electric power is applied.

The operation of the cutting mechanism 140 will be described below. Whenthe monolayers 16A, 16B and 16C are extruded through the T dies 14 a, 14b and 14 c of the multiple T die 14, the monolayers 16A, 16B and 16C arelaminated between the nip rollers 26 a and 26 b of the laminatingmechanism 26 to form the intermediate molten multilayer 16. Theintermediate molten multilayer 16 travels through the space between thepad members 110 of the cutting mechanism 140.

The intermediate molten multilayer 16 is held between the pad members110 at a position about 30 to 100 mm below the die openings of themultiple T die 14 as shown in FIG. 19.

Then, the actuators 146 are actuated to advance the metal thin plate 142which is kept opposite to a surface of the intermediate moltenmultilayer 16. The metal thin plate 142 is pressed against theintermediate molten multilayer 16 as shown in FIG. 21 to cut it tolength by shearing.

During the cutting operation of the cutting mechanism 140, theintermediate molten multilayer 16 is held between the pad members 110 sothat air may not be trapped between the laminated molten monolayers 16A,16B and 16C.

The intermediate molten multilayer 16 can be more easily cut by usingthe heated metal thin plate 142 which is pressed against theintermediate molten multilayer 16.

The actuators 146 retracts the metal thin plate 142 on completion ofcutting operation, and the driving devices 112 retracts the pad members110. When retracting the pad members 110, compressed air is jettedthrough the air passages 118 against the intermediate molten multilayer16. Air blowing at the start of retraction of the pad members enablesthe intermediate molten multilayer 16 to peel off from the surface ofthe pad members 110. Therefore, it is possible to avoid the firmadhesion of the intermediate molten multilayer 16 to the surfaces of thepad members 110.

As for a shape of the half pads 110 a and 110 b of the pad member 110having cooling capability of the cutting mechanism 100, a pair of halfpads which has a shape of a roller may be used.

It is noted that the cutting mechanism 140 can be applied to a processfor cutting a monolayer.

Cutting Mechanism in Third Modification

FIG. 22 shows a cutting mechanism 150 in a third modification.

The cutting mechanism 150 according to the third modification differsfrom the cutting mechanisms 100 and 140 both in disposition andconfiguration. The cutting mechanism 150 is capable of cutting themonolayers 16A, 16B and 16C at positions immediately below the dieopenings of the T dies 14 a, 14 b and 14 c of the multiple T die 14before the monolayers 16A, 16B and 16C are laminated. Therefore, thelaminating mechanism 26 is disposed below the cutting mechanism 150 withrespect to the traveling direction of the intermediate molten multilayer16.

The cutting mechanism 150 is provided with a metal wire 152, preferably,a piano wire, as a cutting means. The metal wire 152 is extended incontact with or close to exits 15 a, 15 b and 15 c of slot openings theT dies 14 a, 14 b and 14 c through which the monolayers 16A, 16B and 16Care extruded. The metal wire 152 is extended by four guide bars 156 a,156 b, 156 c and 156 d so as to be in contact with the exits 15 a, 15 band 15 c of the slot openings of the T dies 14 a, 14 b and 14 c. Themetal wire 152 is extended by the four guide bars 156 a, 156 b, 156 cand 156 d in a plane perpendicular to the width of the monolayers 16A,16B and 16C.

As shown in FIG. 23, the guide bars 156 a, 156 b, 156 c and 156 d areheld on a frame 154. In FIG. 23, only the T die 14 a of the multiple Tdie 14 is shown for simplicity. The metal wire 152 is extended between apair of reels 160 respectively driven for rotation by drive motors 158.One of the pair of reels 160 is a feed reel for feeding the metal wire152 and the other is a take-up reel for taking up the metal wire 152. Apredetermined length of the metal wire 152 is fed out from the feed reel160 and is taken up by the takeup reel 160 for every molding cycle totake up a used section of the metal wire 152 and to feed a new sectionof the metal wire 152 for the next molding cycle.

A metal wire moving mechanism for moving the metal wire 152 extendedbetween the reels 160 along the width of the monolayers 16A, 16B and 16Cwill be described below.

The frame 154, the drive motors 158 and the reels 160 are mounted on aslide block 164 which is supported for sliding along the width of themonolayers 16A, 16B and 16C on guide rails 162. In this modification,the slide block 164 is a rodless cylinder.

The metal wire 152 is preferably heated beforehand by a suitable heatingmeans so that the intermediate molten multilayer 16 will be easily cutthereby. And it is effective to employ a Nichrome wire for the metalwire 152 which generates heat when electrical power is applied.

The action of the cutting mechanism 150 will be described in connectionwith a cutting method. The monolayers 16A, 16B and 16C are extrudedthrough the T dies 14 a, 14 b and 14 c of the multiple T die 14. Theslide block 164 kept on standby near one side end of the monolayers 16A,16B and 16C starts sliding movement along the guide rails 162. The metalwire 152 move along the width of the monolayers 16A, 16B and 16C incontact with the exits 15 a, 15 b and 15 c of the slot openings of the Tdies 14 a, 14 b and 14 c. Consequently, the monolayers 16A, 16B and 16Care cut to a predetermined length simultaneously at the die openings ofthe T dies 14 a, 14 b and 14 c. Thus, the remains of monolayers 16A, 16Band 16C will not be left on the exit 15 a, 15 b and 15 c of the slotopenings of the T dies 14 a, 14 b and 14 c because the parts of themonolayers 16A, 16B and 16C continuous with the exits 15 a, 15 b and 15c of the slot openings of the T dies 14 a, 14 b and 14 c are cut withthe metal wire 152. After cutting the monolayers 16A, 16B and 16C, asection of the metal wire 152 used for cutting them is taken up on thetake-up reel 160 and a new section of the metal wire 152 is extended forthe next cutting cycle. Thus, the monolayers 16A, 16B and 16C can besmoothly cut in the next cutting cycle with the new section of the metalwire 152 which is not caked with the molten polymer.

The pieces of the cut off monolayers 16A, 16B and 16C are nipped betweenthe nip rollers 26 a and 26 b for lamination to provide an intermediatemolten multilayer 16. The intermediate molten multilayer 16 is deliveredto the bottom half mold 24 b of the compression molding machine 18.

FIGS. 24 and 25 shows a cutting mechanism similar in construction to thecutting mechanism 150. The cutting mechanism shown in FIGS. 24 and 25employs a metal thin plate 170 instead of the metal wire 152. As shownin FIG. 24, the metal thin plate 170 is bent and shaped so as to be incontact simultaneously with the end surfaces 15 a, 15 b and 15 c of theT dies 14 a, 14 b and 14 c in which the die openings thereof open. InFIG. 25, only the T die 14 a of the multiple T die 14 is shown forsimplicity. The metal thin plate 170 is held on the frame 154 capable ofmoving along the width of the monolayers 16A, 16B and 16C. In FIG. 25,parts like or corresponding to those shown in FIG. 23 are designated bythe same reference characters and the description thereof will beomitted.

Cutting Process and Cutting Mechanism in Fourth Modification

FIGS. 26( a), 26(b) and 26(c) shows different phases of a cuttingprocess for the intermediate molten multilayer 16 which is differentfrom the cutting process of the foregoing embodiments. This cuttingprocess does not use any cutting means. Alternatively, a piece of theintermediate molten multilayer 16 is pulled off by using the nip rollers182 a and 182 b of a laminating mechanism 182 so that a part of themonolayers 16A, 16B and 16C near the die openings of the T dies 14 a, 14b and 14 c is torn off.

The laminating mechanism 182 for laminating the monolayers 16A, 16B and16C extruded through the T dies 14 a, 14 b and 14 c of the multiple Tdie 14 to form the intermediate molten multilayer 16 is disposed belowthe multiple T die 14.

The laminating mechanism 182 serves also so as a pulling and cuttingmeans for pulling the intermediate molten multilayer 16 and tearing itoff at the die openings of the T dies 14 a, 14 b and 14 c.

Referring to FIGS. 26( a), 26(b) and 26(c), the pair of nip rollers 182a and 182 b are disposed opposite to each other near the die openings ofthe T dies 14 a, 14 b and 14 c. The monolayers 16A, 16B and 16C extrudedthrough the T dies 14 a, 14 b and 14 c are nipped between the niprollers 182 a and 182 b so that any air may not be trapped between thelaminated layers to form the intermediate molten multilayer 16. The niprollers 182 a and 182 b, similarly to those of the foregoingembodiments, move together with the multiple T die 14.

Referring to FIG. 27 showing the laminating mechanism 182, supportshafts 184 a and 184 b projecting from the opposite ends of the pair ofnip rollers 182 a and 182 b are supported for rotation in bearings 186,respectively. Driven pulleys 188 a and 188 b are mounted on the supportshafts 184 a and 184 b, respectively, and drive pulleys 192 a and 192 bare mounted on the output shafts of drive motors 190 a and 190 b atpositions opposite the driven pulleys 188 a and 188 b, respectively.Synchronous belts 194 a and 194 b are wound around the driven pulley 188a and the drive pulley 192 a, and around the driven pulley 188 b and thedrive pulley 192 b, respectively. A actuators 196, such as pneumaticcylinder actuators, are connected properly to the support shafts 184 aand 184 b to move the opposite nip rollers 182 a and 182 b toward andaway from each other.

Operations of the multiple T die 14, and the nip rollers 182 a and 182 bduring a laminating process and a cutting process will be describedhereinafter.

As shown in FIG. 26( a), the monolayers 16A, 16B and 16C are extrudedthrough the T dies 14 a, 14 b and 14 c while the multiple T die 14 isbeing advanced. Upon the detection of the leading edges of themonolayers 16A, 16B and 16C which past the space between the nip rollers182 a and 182 b by a sensor, not shown, the actuators 196 move the niprollers 182 a and 182 b toward each other. The monolayers 16A, 16B and16C are compressed between the nip rollers 182 a and 182 b so that theintermediate molten multilayer 16 is formed.

The multiple T die 14 is advanced to a position corresponding to thefront ends of the mold 24 a, 24 b of the compression molding machine 18as shown in FIG. 26( a). The drive motors 190 a and 190 b drives the niprollers 182 a and 182 b for rotation in the directions of the arrows,respectively. Consequently, the leading edge of the intermediate moltenmultilayer 16 reaches one end of the bottom half mold 24 b. Upon thedetection of the arrival of the leading edge of the intermediate moltenmultilayer 16 by a suitable sensor, not shown, a holding member 200included in the mold changing device 36 is operated to hold a endportion of the intermediate molten multilayer 16 fixedly on one end ofthe bottom half mold 24 b.

Subsequently, as shown in FIG. 26( b), the multiple T die 14 is movedbackward together with the laminating mechanism 182. The nip rollers 182a and 182 b are rotated at a rotating rate corresponding to the movingrate of the multiple T die 14 in order that a laminating rate at whichthe intermediate molten multilayer 16 is delivered coincides with a feedrate at which the multilayer 16 is fed onto the bottom half mold 24 b.

As shown in FIG. 26( c), upon the arrival of the multiple T die 14 at aposition at a short distance from a position corresponding to the backends of the mold 24 a, 24 b, the extrusion of the molten polymersthrough the T dies 14 a, 14 b and 14 c of the multiple T die 14 issuspended and, at the same time, the rotation of the nip rollers 182 aand 182 b holding the intermediate molten multilayer 16 therebetween isstopped. Then, the rotation of the nip rollers 182 a and 182 b isresumed at the rotating rate for delivering the intermediate moltenmultilayer 16 or at a rotating rate suitable for tearing it off.Consequently, That makes it possible to tear off monolayers 16A, 16B and16C simultaneously at the die openings of the T dies 14 a, 14 b and 14c. The cut edges of the monolayers 16A, 16B and 16C are welded together.After the monolayers 16A, 16B and 16C has been cut, the rotation of thenip rollers 182 a and 182 b is suspended, and the nip rollers 182 a and182 b are moved away from each other. The multiple T die 14 retreatsbeyond the back ends of the mold 24 a, 24 b to its standby position.Meanwhile, the compression molding machine 18 operates for compressionmolding to form the intermediate molten multilayers 16 into a moldedmultilayer article.

Preferably, the surface of the nip rollers 182 a and 182 b are coatedwith anti-adhesive coatings to avoid the adhesion of the moltenpolymers. Preferably, the nip rollers 182 a and 182 b are internallyprovided with temperature control means including coolant passages, notshown, to keep the nip rollers 182 a and 182 b at a predeterminedtemperature while the intermediate molten multilayer 16 is held betweenthe nip rollers 182 a and 182 b. Scrapers 202 a and 202 b may bedisposed in combination with the nip rollers 182 a and 182 b as shown inFIG. 26( b) or blowing means may be combined with the nip rollers 182 aand 182 b to ensure the separation of the intermediate molten multilayer16 from the nip rollers 182 a and 182 b.

Thus, the monolayers 16A, 16B and 16C extruded through the T dies 14 a,14 b and 14 c of the multiple T die 14 can be laminated by compressingthe same between the nip rollers 182 a and 182 b to form theintermediate molten multilayer 16. Since the nip rollers 182 a and 182 bpulls monolayers 16A, 16B and 16C tear them off at the die openings ofthe T dies 14 a, 14 b and 14 c, any air may not be trapped between thelaminated monolayers 16A, 16B and 16C. Accordingly, the intermediatemolten multilayer 16 properly laminated can be smoothly delivered to themold of the compression molding machine 18.

Cutting Mechanism in Fifth Modification

FIGS. 28 and 29 show a cutting mechanism 210 in a fifth modification.

The cutting mechanism 210 have basically a similar function to that ofthe cutting mechanism 150 in the third modification which is capable tocutting the monolayers 16A, 16B and 16C at the die openings of the Tdies 14 a, 14 b and 14 c of the multiple T die 14 before the monolayers16A, 16B and 16C are laminated.

Referring to FIG. 28, cutting members 214 a, 214 b and 214 c are held ona bracket 212 which is attached to a front end of a swing plate 216. Theswing plate 216 is supported for swinging by a support shaft 218 onbrackets 220.

The swing plate 216 is turned to bring the cutting members 214 a, 214 band 214 c into contact with or to separate the same from the exits 15 a,15 b and 15 c of the slot openings of the T dies 14 a, 14 b and 14 c inwhich the die openings open. The swing plate 216 is forced by a spring222 to bring the cutting members 214 a, 214 b and 214 c into contactwith the end surfaces 15 a, 15 b and 15 c of the T dies 14 a, 14 b and14 c, respectively.

The cutting members 214 a, 214 b and 214 c, the bracket 212, the swingplate 216, the support shaft 218 and the brackets 220 constitute acutting unit. A cutter moving mechanism for moving the cutting unit isshown in FIG. 29, in which only the T die 14 a of the multiple T die 14is shown for simplicity.

The brackets 220 of the cutting unit is attached to a slide block 226supported for sliding on guide rails 224 extended in parallel to thewidth of the monolayers 16A, 16B and 16C. In this modification, arodless cylinder unit is applicable to the the slide block 226.

An eccentric guide bar 228 is extended with its geometric center axis inparallel to the guide rails 224. The eccentric guide bar 228 is providedin its circumference with a first cam groove 230 a and a second camgroove 230 b extending in the longitudinal direction. A cam follower 232fixed to the swing plate 216 is in engagement with the first cam groove230 a as shown in FIG. 28.

In FIG. 29, the slide block 226 is at its standby position. Whenmonolayers 16A, 16B and 16C, the cam follower 232 moves along the firstcam groove 230 a. When the slide block 226 is moved backward for areturn stroke after the monolayers 16A, 16B and 16C have been cut, thecam follower 232 moves along the second cam groove 230 b.

Since the cam follower 232 moves along the first cam groove 230 a andthe second cam groove 230 b, the eccentric guide roller 228 is turnedthrough an angle of 90 degrees by every travel of the slide block 226.As is obvious from FIG. 28, the shaft of the eccentric guide roller 228is displaced by a predetermined eccentricity from the geometric centerof the eccentric guide bar 228 so that the second cam groove 230 b isincluded in a plane including a radius longer than a radius included ina plane including the first cam groove 230 a.

The action of the cutting mechanism 210 will be described in connectionwith a cutting method.

The monolayers 16A, 16B and 16C are extruded through the T dies 14 a, 14b and 14 c of the multiple T die 14. The slide block 226 starts off on asliding travel from the standby position along the guide rails 224. Atthis stage, the eccentric guide bar 228 is at an angular position shownin FIG. 28. As the slide block 226 moves forward for a cutting stroke,the cam follower 232 moves along the first cam groove 230 a. Therefore,the cutting members 214 a, 214 b and 214 c held on the bracket 212attached to the end part of the swing plate 216 move in contact with theexits 15 a, 15 b and 15 c of the slot openings of the T dies 14 a, 14 band 14 c along the width of the monolayer 16A, 16B and 16C.Consequently, the monolayers 16A, 16B and 16C are cut off simultaneouslyat the die openings of the T dies 14 a, 14 b and 14 c. Thus, the remainsof monolayers 16A, 16B and 16C will not be left on the exits 15 a, 15 band 15 c of the slot openings of the T dies 14 a, 14 b and 14 c.

In a final stage of the cutting operation, the slide block 226 reachesthe front end of the cutting stroke, and the cam follower 232 is forcedto move from the first cam groove 230 a to the second cam groove 230 band, consequently, the eccentric guide bar 228 is turnedcounterclockwise, as viewed in FIG. 28, through an angle of 90.

Since the shaft of the eccentric guide bar 228 is displaced from thegeometric center of the guide bar 228 by the predetermined eccentricityε, the swing plate 216 is turned slightly counterclockwise, as viewed inFIG. 28, through the cam follower 232. Consequently, the cutting members214 a, 214 b and 214 c shift its position so as to be apart from theexits 15 a, 15 b and 15 c of the slot openings of the T dies 14 a, 14 band 14 c.

Then, the slide block 226 is moved backward for return stroke to thestandby position with the cam follower 232 being engaged with the secondcam groove 230 b. The cutting members 214 a, 214 b and 214 c maintains aposition apart from the exits 15 a, 15 b and 15 c of the slot openingsof the T dies 14 a, 14 b and 14 c. Therefore, the molten polymers oozingthrough the die openings of the T dies 14 a, 14 b and 14 c will notadhere to the cutting members 214 a, 214 b and 214 c, and the monolayers16A, 16B and 16C can be smoothly cut with the cutting members 214 a, 214b and 214 c free from adherent polymers in the next cutting cycle.

The monolayers 16A, 16B and 16C thus cut off are compressed forlamination between the nip rollers 26 a and 26 b of the laminatingmechanism 26 to shape them into an intermediate molten multilayer 16,which is delivered onto the bottom half mold 24 b of the compressionmolding machine 18.

Although the invention has been described in its preferred forms with acertain degree of particularity, various changes and variations may bemade in the design thereof without departing from the scope and spiritof the invention.

For example, the molded multilayer article manufacturing apparatus maybe provided, instead of the injection molding unit as a plastificationmeans, with an extruder provided with plungers and capable ofintermittently extruding molten polymers like the injection moldingmachine.

The molded multilayer article manufacturing apparatus may be providedwith a guide means including guide rails disposed on a fixed platemounted with the bottom half mold so as to extend over the bottom halfmold to guide the multiple T die, the laminating mechanism, and thecutting mechanism for simultaneous movement toward and away from themold of the compression molding machine. The guide means ensures thestable, reliable movement of the multiple T die toward and away from themold in synchronism with the operation of the injection molding machine.Stable molding operation can be achieved even if the heavy combinationof the multiple T die and the laminating mechanism is supported on thedelivery nozzles of the injection molding machine in a cantileverfashion.

1. A method for manufacturing a molded multilayer article by molding amultilayer sheet consisting of a plurality of polymer layers,comprising: extruding a plurality of monolayers of molten polymers byforcing the molten polymers into a multiple T die formed by an assemblyof T dies so that the molten polymers are extruded from slot openings ofrespective T dies forming the assembly; forming an intermediate moltenmultilayer by superposing and laminating the monolayers extruded throughthe T dies outside the respective T dies while the polymers are in amolten state or a semi-molten state; feeding the intermediate moltenmultilayer to a compression mold having a bottom half mold and a tophalf mold by advancing the multiple T die into a space between thebottom half mold and the top half mold; cutting the intermediate moltenmultilayer to a predetermined length; and molding the intermediatemolten multilayer in the compression mold into a multilayer article of adesired shape, wherein the intermediate molten multilayer is cut in aplane including an exit of a slot opening of the respective T dies, andwherein a cutting process comprises: extending a metal wire in a planeintersecting a plane including the intermediate molten multilayer so asto be able to be brought into contact with end surfaces of the T dies ofthe multiple T die in which the die openings of the T dies open; andmoving the metal wire along the end surfaces of the T dies along thewidth of the intermediate molten multilayer.
 2. The molded multilayerarticle manufacturing method according to claim 1, wherein a movingoperation for moving the metal wire accompanies by heating the metalwire, and taking up a length of the metal wire.
 3. A method formanufacturing a molded multilayer article by molding a multilayer sheetconsisting of a plurality of polymer layers, comprising: extruding aplurality of monolayers of molten polymers by forcing the moltenpolymers into a multiple T die formed by an assembly of T dies so thatthe molten polymers are extruded from slot openings of respective T diesforming the assembly; forming an intermediate molten multilayer bysuperposing and laminating the monolayers extruded through the T diesoutside the respective T dies while the polymers are in a molten stateor a semi-molten state; feeding the intermediate molten multilayer to acompression mold having a bottom half mold and a top half mold byadvancing the multiple T die into a space between the bottom half moldand the top half mold; cutting the intermediate molten multilayer to apredetermined length; and molding the intermediate molten multilayer inthe compression mold into a multilayer article of a desired shape,wherein the intermediate molten multilayer is cut in a plane includingan exit of a slot opening of the respective T dies, and wherein acutting operation for cutting the intermediate molten multilayercomprises: disposing a plurality of cutting members in a planeintersecting the intermediate molten multilayer so as to be able to bebrought into contact with the exit of the slot opening of the T dies ofthe multiple T die; and reciprocating the cutting members along the exitof the slot opening of the T dies in directions parallel to the width ofthe multilayer sheet.
 4. The molded multilayer article manufacturingmethod according to claim 3, wherein a reciprocating operation forreciprocating the cutting members comprises: holding the cutting membersin sliding contact with the exit of the slot opening of the T dies andmoving the cutting members for a cutting stroke along the width of theintermediate multilayer to cut it off; and moving the cutting membersfor a return stroke to their initial positions while separating thecutting members from the exit of the slot opening of the T dies.
 5. Amethod for manufacturing a molded multilayer article by molding amultilayer sheet consisting a plurality of polymer layers, comprising:extruding a plurality of monolayers of molten polymers by forcing themolten polymers into a multiple T die formed by an assembly of T dies sothat the molten polymers are extruded respectively through slots ofrespective T dies forming the assembly; passing the monolayers extrudedthrough the T dies through a space between a pair of nip rollersdisposed opposite to each other; forming an intermediate moltenmultilayer by superposing and laminating the monolayers outside themultiple T die by pressing the monolayers between the pair of rotatingnip rollers while the polymers are in a molten state or a semi-moltenstate; advancing the pair of nip rollers together with the multiple Tdie into a space between an open top half mold and a bottom half mold ofa compression mold while a laminating operation of the pair of niprollers is continued; fixing a front end portion of the intermediatemultilayer to one end of the bottom half mold of the compression mold;moving the pair of nip rollers together with the multiple T die backwardwhile a laminating operation of the pair of nip rollers is continued;stopping the rotation of the pair of nip rollers and stopping theextrusion of the molten polymers while the pair of nip rollers are movedcontinuously backward in order to cut the intermediate moltenmultilayer; and molding the intermediate molten multilayer molding inthe compression mold into a multilayer article of a desired shape.